1. Field of the Invention
The present invention generally relates to an image forming unit and image forming device. More specifically, the present invention relates to an image forming unit that includes a rotation speed control device that controls the rotation speed of a rotary developing device and an image forming device that includes such an image forming unit.
2. Background Information
Image forming devices that form color images include a plurality of developing apparatuses that each house toner of a different color. Some image forming devices that form color images have rotary developing devices in which the plurality of developing apparatus is fitted around a rotatable frame. In an image forming device that uses a rotary developing device, the frame is rotated and the developing apparatus that houses the developer with the first color is brought into opposition with an electrostatic latent image carrier, and the developer in the developing apparatus is supplied to the electrostatic latent image carrier. After the developer for the first color has been supplied to the electrostatic latent image carrier, the frame is rotated and the developing apparatus that houses the developer with the second color is brought into opposition with the electrostatic latent image carrier, and the developer in the developing apparatus is supplied to the electrostatic latent image carrier. In this way, developer is supplied to the electrostatic latent image carrier in turn so that developer for all the colors is supplied to the electrostatic latent image carrier.
Here, when supplying developer from the developing apparatus to the electrostatic latent image carrier, there is a system in which the developer on a developing roller is supplied to the electrostatic latent image carrier without the developing roller contacting the electrostatic latent image carrier. In image forming devices that adopt this system, a distance regulating collar whose diameter is slightly larger than the diameter of the developing roller is provided at both ends of the developing roller in the axial direction. The distance regulating collars contact the electrostatic latent image carrier so a gap is maintained between the developing roller and the electrostatic latent image carrier as shown in Japanese Patent Application Laid-open No. H11-174826.
In the image forming device described in the aforementioned patent document, to prevent the distance regulating collars from applying shocks to the surface of the electrostatic latent image carrier as a result of the electrostatic latent image carrier and the distance regulating collars contacting at different movement speeds in the circumferential direction, the movement speed in the circumferential direction of the distance regulating collars is reduced before the electrostatic latent image carrier and the distance regulating collars contact. Then contact is made at the instant that the movement speed in the circumferential direction of the electrostatic latent image carrier and the distance regulating collars is the same.
However, in the image forming device described in the patent document, the phase speed in the circumferential direction of the distance regulating collars is reduced continuously so the movement speed in the circumferential direction of the electrostatic latent image carrier and the distance regulating collars is the same only for an instant. Therefore, if even a small error occurs the movement speed in the circumferential direction of the electrostatic latent image carrier and the distance regulating collars will be different, and a shock will be applied to the electrostatic latent image carrier by the distance regulating collars. When a shock is applied to the electrostatic latent image carrier in this way, the photosensitive layer of the electrostatic latent image carrier can peel off, and the electrostatic latent image carrier can become deformed. Therefore, a constant distance between the developing roller and the electrostatic latent image carrier cannot be maintained, and image quality can be reduced by unevenness in the image and so on.
In view of the above, it will be apparent to those skilled in the art from this disclosure that there exists a need for an improved image forming device. This invention addresses this need in the art as well as other needs, which will become apparent to those skilled in the art from this disclosure.